1. Field of the Invention
The present invention relates to control circuitry utilized for automatically interrupting the flow of a combustible gas to a zone of ignition and combustion at such time as an igniting element used to ignite the gas as inactive. More particularly, the present invention relates to electrical control circuitry employed to continuously monitor and detect the status of a firing circuit used to develop sparks for the purpose of igniting combustible gas delivered to a gas burner in close proximity to the sparks, and providing a heat source as a result of combustion of the gas.
2. General Description of the Need
In a number of industrial devices, systems are provided which use as a heat source, a combustible gas, such as propane, which is burned upon ignition by an ignition spark provided adjacent a gas burner from which the combustible gas is discharged. A safety hazard is encountered in systems of this type in the event of malfunction of the firing circuit by which the spark is developed, in that the combustible gas may be inadvertently turned on or left on at a time when there is no source of ignition of the gas. This is often due to inactivation or failure of the firing circuit to provide the igniting spark, and the combustible gas discharges into the surrounding atmosphere and becomes admixed with the air in explosive proportion. It is often difficult to know, with certainty, without close scrutiny, whether the firing circuit by which the igniting spark is developed is operating properly. Moreover, with a careless operator of the system, the operator sometimes fails to energize the sparking circuit until gas has been discharging into the air adjacent the spark-generating device for several seconds.
3. Brief Description of the Present Invention
The present invention provides a spark-monitoring control system by which the flow of gas to a gas burner is controlled to assure that no gas escapes from the burner to the atmosphere when the firing circuit included in the system is inoperative to develop an igniting spark.
The invention can be broadly described as including an RF antenna positioned to detect radio frequency noise signals developed by the generation of a spark by a spark-generating device, which antenna is connected through a detector and filter network to an amplifier. The received signal is amplified and is employed to energize the coil of a sensitive relay. Energization of the relay closes a switch in a circuit containing a solenoid fuel valve. This status of the circuit energizes the normally closed solenoid control valve to open the valve, and permit fuel to flow to the burner where it is ignited by the spark. When the spark is inoperative, no signal is detected by the antenna, and the relay is not energized. Accordingly, the relay-operated switch in the solenoid valve electrical circuit remains open, and the solenoid valve remains de-energized and closed, thus preventing the discharge of combustible gas from the burner.
An important object of the invention is to provide a simple electrical circuit used in combination and association with a sparking device and a combustible gas burner to control the flow of gas to the burner in response to the operative status of the sparking device.
Another object of the invention is to improve the operational safety of heating devices which employ combustible gases ignited by a generated spark.
Additional objects and advantages of the invention will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawing which illustrates the circuitry used in conjunction with a gas burner and a spark-generating device in the present invention.